Note: there was no need to delete partition prior to blkdiskard execution and after it was done kernel (lsblk) noticed the changes (that there is no partition anymore)
---------
cd /home/emacs && time sudo blkdiscard -s -v /dev/sdb
[sudo] password for emacs: 
blkdiscard: /dev/sdb: BLKSECDISCARD ioctl failed: Operation not supported

real  0m1.920s
user  0m0.047s
sys 0m0.010s
-----------
emacs@manji 2014/10/18 07:14:26 bash4.3.30 t:3 j:0 d:2 pp:13499 p:13500
!44075 3 1 3.17.0-g0429fbc #157 SMP Thu Oct 16 13:50:59 CEST 2014 $
cd /home/emacs && time sudo blkdiscard -v /dev/sdb
/dev/sdb: Discarded 1000204886016 bytes from the offset 0

real  0m2.402s
user  0m0.023s
sys 0m0.007s

